/* one element includs another */
.aaa .bbb{width:100px;}
/* one element includs another */
.aaa >.bbb{width:100px;}
/* one element includs another */
.aaa> .bbb{width:100px;}
/* have two classes in one element */
.aaa.bbb{height:100px;}

/* one element includs another */
#ccc #ddd{width:100px;}
/* one element includs another */
#ccc >#ddd{width:100px;}
/* one element includs another */
#ccc> #ddd{width:100px;}
/* have two classes in one element */
#ccc#ddd{height:100px;}